US3545410A - Steam generating installations - Google Patents

Steam generating installations Download PDF

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Publication number
US3545410A
US3545410A US768390A US3545410DA US3545410A US 3545410 A US3545410 A US 3545410A US 768390 A US768390 A US 768390A US 3545410D A US3545410D A US 3545410DA US 3545410 A US3545410 A US 3545410A
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United States
Prior art keywords
steam
circuit
circulation
tube
water
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Expired - Lifetime
Application number
US768390A
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English (en)
Inventor
Eric Maurice Woolley
George Wright
Roy Crisp
Robert Dennis Atkinson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Head Wrightson and Co Ltd
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Head Wrightson and Co Ltd
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Filing date
Publication date
Priority claimed from GB4788167A external-priority patent/GB1207688A/en
Application filed by Head Wrightson and Co Ltd filed Critical Head Wrightson and Co Ltd
Application granted granted Critical
Publication of US3545410A publication Critical patent/US3545410A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/1823—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines for gas-cooled nuclear reactors

Definitions

  • This invention relates to steam generating installations and is concerned with installations of the type, hereinafter referred to as of the type described," in which heat, for example waste heat from a steel-making process, is supplied intermittently to a stack incorporating evaporatively cooled surfaces, the steam being passed to thesteam drum of the steam generating circuit of the installation.
  • Natural circulation has the disadvantage that, when this is the only method of circulation, the water in the circuit will be stagnant at the time that heat is first supplied to the evaporatively cooled surfaces.
  • this heat input is brought on gradually at the commencement of an operation.
  • the heat is subjected to an on/off control system, but the heat fluxes experienced are not abnormally high.
  • a pumped circulation system has the advantage of ensuring that when sudden heat input occurs, this will occur on existing circulation within the cooling circuit. Because pumped circu lation is used, a higher friction resistance can be permitted in the circuit, and this permits the use of smaller bore tubing, with a resultant saving in weight.
  • the amount waterflow apportioned to each heated tube is governed by the sizing of an orifice. The heat flow is calculated, and the waterflow matched, so that an acceptable calculated ratio of steam/water will be present at the outlet from the heated tube. For those cases where the water entering the tube is well below the boiling temperature, the orifice additionally ensures stability of flow and correct division of flow between the several tubes connected in parallel.
  • the pumped circulation system can save weight by using smaller bore tubes, this also has the disadvantage of reducing the thermal reservoir capacity of the water contained in the tube. Should the heat input in practice exceed that calculated, it is easier .to obtain a dry out condition in these smaller bore tubes. Such a case can arise more easily in than other adjacent tubes, e.g. through particular flame t impingement, then the relative flow through these tubes under natural circulation is mainly self-adjusting, automatically matching circulation to heat input, by the very nature of its design.
  • the method initially calls for operation on the pumped circulation principle and thereafter operates on the natural circulation principle.
  • the method according to the invention also comprises the step of storing the said steam which is injected into the circuit in a accumulator which is arranged to operate in parallel with the site steam main.
  • an installation of the type described which comprises one or more devices arranged in the steam circuit between the evaporatively cooled surfaces and the steam drum which devices are arranged to inject a supply of steam into the circuit in order to raise the temperature therein, and to promote circulation, so as to reduce thermal stresses particularly in the evaporatively cooled surfaces.
  • a further feature of the invention is that means are provided for terminating the supply of steam to the said devices when the circuit reaches a predetermined condition.
  • a steam accumulator which is capable of supplying steam to said devices at any time during the norrnall operation of the cyclic systems receiving intermittent and sudden high-heat fluxes
  • the larger tubes used in natural circulation provide both a larger mass of water within the tube, and a greater freedom for the suddenly formed steam bubbles on the tube wall to be accommodated within the rising steam/water mixture.
  • Natural circulation has a further advantage over the orifice controlled flow pumped circulation in that it is much more flexible; should, therefore, particular tubes receive more heat heat input equipment of the installation, said accumulator being arranged to operate in parallel with the site steam main.
  • FIG; 1 is a schematic layout of part of an installation according to the invention, a
  • FIG. 2 is a schematic layout of a continuation of FIG. I the two parts being joined together at the points marked fX,
  • FIG. 3 is a section through one form of assistant circulator device
  • FIG. 4 is a section, on an enlarged scale, on the line 4-4 of FIG. 3, and
  • FIGS. 5 to 9 are sections through alternative forms of assistant circulator devices.
  • the installation comprises a flue or stack 10, the walls of which are provided with evaporatively cooled surfaces, for example evaporatively cooled tubular panels, the flue or stack 10 being arranged to receive heat intermittently from a source of supply 11 which may, for example, be a steel making converter.
  • a source of supply 11 which may, for example, be a steel making converter.
  • the drawing shows the panels of the flue or staclk 10 as being in three separate sections but it will of course be appreciated that one or more panel sections may be provided according to requirements.
  • Each panel section is connected to an outlet header 12 from which a steam/water mixture passes, via riser pipes 13, to a steam drum 14.
  • Steam is passed from the steam drum via a pipe 15 and feed water is passed into the steam drum 14 through a pipe 16 a steam drum overflow isindicated at 17.
  • Water from the steam drum 14 is passed, via a downcomer l8 and inlet headers 19, to the evaporatively cooled panels.
  • assistant circulators are arranged to inject steam into each of the riser pipes 13, the steam being passed through supply pipes 21, each incorporating a nonretum valve 22, via common supply lines 23 and 23a under the control of flow control valves 24 or 24a.
  • the common supply line 23a carries steam from site or from another source such as a suitable package boiler.
  • the invention is primarily concerned with maintaining correct conditions in an established or working installation, it also provides advantages where the installation is to be started up from cold.
  • the flow control valve 24a When the pressure in the steam drum 14 reaches the minimum accepted operating pressure, the flow control valve 24a will be closed, and the further flow control valve 24 preferably of a larger capacity can be opened. This valve is opened just before the system is due to receive heat from the heat supply source 11. As the water is now at saturation condition the steam bubbles coming from the assistant circulators 20 will, therefore, cause a steam/water mixture to exist in the riser pipes 13, thereby setting up a more vigorous circulation in the system due to the density differential existing between the water in the downcomer 18 and the steam/water mixture in the riser pipes 13. Steam will be bled from the drum 14 as required, in order to maintain sufficient driving pressure for the circulators.
  • the pressure in the steam drum 14 can be permitted to rise at a controlled rate.
  • the valves 22 will close shutting off steam to the assistant circulators 20. From this point of time forward the system operates completely as a natural circulation system, while the heat input continues.
  • the installation may further include a main steam storage accumulator 25 which is provided, in generally known manner, to receive steam in excess of site requirements and is, for this purpose, connected via lines 26 and27 in parallel with the site steam main l5.
  • Condensers 28 are also arranged via line 29 in the site steam and accumulator circuit and provide a feed water supply which passes to the steam drum 14 via the pipe 16 using a feed pump.
  • steam for supplying the assistant circulators 20 is stored in an assistant accumulator 30.
  • the supply pipes 21 are in communication with the supply line 23 which is connected to the accumulator 30 by a line 31.
  • the accumulator 30 is further connected, via steam lines 32, to the site steam main 15.
  • the installation incorporating the accumulators 25 and 30 operates as follows:
  • the cooling circuit comprising items 14, 18, 10, 20 and 13 has been filled up with cold water
  • the circuit is at atmospheric pressure.
  • Steam is then admitted to the circuit via the steam lines 23 and 23a, and the assistant circulators 20, at first raising the temperature of the circuit to boiling point at atmospheric pressure.
  • Continuation of the steam supply via the circulators 20 will gradually raise the pressure and temperature of the water and the temperature of the metallic members carrying the water through the circuit, until it reaches a pressure approaching that of the supply source which, in this case, is steam from the site which is passed thereto via line 23a.
  • the rising steam bubbles from the assistant circulators 20 in the riser pipes 13 will cause circulation of the water in the circuit of sufficient rate to permit the initiation of the am main heat source 11.
  • the assistant accumulator 30 is connected in parallel with the now heated circuit via the lines 2l, 23, 31 and 32 the line 32 including a nonretum valve 33.
  • the size of the accumulator 30 is such that it will rise in pressure at the same rate as the heated circuit and store, for a relatively small pressure rise, all the steam needed for the operation of the assistant circulators 20.
  • the assistant circulator accumulator 30 is sized so that it can amply provide circulation of the water at the beginning, and just prior to, the commencement of the heat input, and continue the operation so there exists a reasonable overlap period of the operation of the assistant circulators 20, with the commencement of heat input.
  • valve 34 Under normal operative conditions a valve 34 will be opened by a signal which, with a slight time lag, also initiates the heat input source 11, such that it always follows behind, in time, the commencement of the flow of steam through the assistant circulators 20. Control of the valve 34 is such that it maintains a relatively constant flow of steam into the circuit.
  • the heat input then commences and the steam generated will cause a rise in system pressure.
  • the control system is such that the rate of system pressure rise is controlled to a rate acceptable to the pressure parts.
  • the assistant accumulator pressure will rise at the same rate.
  • the steam pressure in the circuit is allowed to fall at a controlled rate thereby performing two functions in that, firstly, it releases steam stored in the circuit to thesite as it drops in pressure, and secondly, as the pressure drops, it causes the water to be maintained at boiling temperature throughout the circuit, thus avoiding the undesirable existence of uneven temperature distribution as i well as excessive subcooled water throughoutthe circuit, i.e.
  • the steam accumulation in the circuitry is also such that it enables steam to be distributed to the site over a wide cycle of operation.
  • the evaporatively cooled walls can be of the more robust construction associated with the larger bore tubes of a natural circulationsystem, coupled with the related advantages of an increased thermal reservoir capacity, while avoiding the disadvantages of the pumped system.
  • the assistant circulators should be designed so that the injection nozzles thereof avoid an injection location which can cause steamslugging to occurat the point of entry of the induced waterflow, and should comply with the following? 1.
  • Steam injection should occur insulch mannerthat the ini cuted waterflow is concentric and in parallel flow, in a straight vertical part of the riser tube, with the steam injection entry, preferably at the center of the riser tube, in
  • the steam nozzle injection holes should be of small diameter and meet the requirements I concerning clearance as hereinafter described.
  • the core of the injection nozzle should be packed with steel wool, or the equivalent, as also should the space between the nozzle and the nozzle branch entry pipe, where applicable.
  • an assistant circulator comprises an arc'uate tube section 35 which is coupled to, or forms part of, each riser tube 1.3, the tube section 35 being formed with a branch entry pipe 36which is disposed tangentially with respect thereto.
  • an injection tube guide plate 39 At the junction of the tube section 35 and the branch pipe 36 there is provided an injection tube guide plate 39, the branch pipe being packed with stainless steel wool or the equivalent indicated at 40.
  • the injection tube 37 is adapted to be connected to the steam line 21 and is also packed with stainless steel wool or the equivalent indicated at 41. t
  • the injection nozzle 38 is tapered and is drilled with smal diameter holes 42 which are inclined upwardly so as to facilitate the rising flow of small bubbles of steam in the direction of the arrows 43.
  • the vertical pitch p of the holes42 is such that there exists, in plain view, a clearance c from one set of holes to the next adjacent set.
  • Thenozzle 38 is formed with four spaced longitudinally disposed stifi'ener plates and guide vanes 44, and is closed at its forward end by a cap 45.
  • the steam injection tube is located, at its forward end, concentrically within the tube section 35 by means of four adjustable steady rods 46 which engage the edges of the stiffener plates 44 which, for this purpose, are provided with reinforcing blocks 47.
  • a closure plate 48 for the branch pipe 36 which plate is fixed to the tube 37, is adapted to be located by two dowel pins 49 provided at different centers on a flange 50 fixed to the pipe 36.
  • FIG. shows another form of assistant circulator in which steam is passed into the tube section 35 via a stuffing box 51 packed with wire wool or the like 52, the forward end of the stuffing box 51 being provided with an apertured plate 53 arranged so that the steam pa'sses into the waterflow in the same direction as the movement of said flow.
  • FIG. 6 shows an arrangement similar to FIG. 3 but of simplified form.
  • FIGS. 7, 8 and 9 show further forms of circulators where the branch pipe is dispensed with and steam in injected into the tube section 35 through a transversely disposed pipe 54 which is adapted to be coupled to the line 21.
  • the pipe 54 is connected to a crossflow nozzle 55 which extends across the diameter of the tube section 35 and is formed with apertures 56 through which steam is passed into the waterflow.
  • the pipe 54 is connected to a nozzle ring 57 arranged within the tube section 35 and having apertures 58 through which the steam is passed'into the waterflow.
  • the pipe is connected to an annular venturi type nozzle 59 arranged within the tube section 35 and having apertures 60 through which the steam is passed into the waterflow.
  • a steam generating installation comprising a stack adapted to be intermittently supplied with an external heated medium, said stack including evaporation means including evaporatively cooled surfaces, a steam drum located above said stack, first conduit means for conducting cooling water from said steam drum to said evaporation means, second conduit means for conducting a steamwater mixture from said evaporation means to said steam drum, and means for injecting steam into said second conduit means at a position below said steam drum sufficient to establish a density differential between the cooling water in said first conduit means and the steam-water mixture in said second conduit means to achieve circulation in the system from said evaporation means through said second conduit means to said steam drum prior to the supplying of the heated medium to the stack thereby reducing thermal stresses in the system and particularly the evaporation means thereof.
  • the steam generating installation as defined in claim 1 including means for retarding the flow of steam through said steam injection means whereby the steam, when injected into said steam-water mixture, is reduced to a ms mass of small diameter bubbles, and said retarding means is intersticesdefining means housed within said steam injection means.
  • the steam generating installation as defined in claim 1 including means for intermittently supplying the external heated medium to the stack.
  • the steam generating installation as defined in claim 1 including an onsite source of steam, and means coupling said onsite source of steam to said steam injection means.
  • the steam generating installation as defined in claim 1 including a small package boiler for supplying steam to said steam injecting means.
  • the steam generating installation as defined in claim 1 including steam accumulator means for supplying steam to said steam injecting means.
  • said steam injection means comprises a tube section connected'to said second conduit means, a branch pipe extending generally tangentially with respect to said tube section, a steam injection tube extending through said branch pipe and into said tube section, said steam injection tube having an apertured nozzle disposed in a straight portion of said tube section, and at least one of said branch pipe and said in jection tube being packed in with means defining interstices for retarding the passage of steam therethrough.
  • the steam generating installation as defined in claim 10 including adjustable steady rods for positioning the steam injection tube generally centrally of the tube section.
  • said steam injecting means includes a tube section connected to said second conduit means, a tangentially disposed stuffing box attached to said tube section for receiving steam from a steam source, an apertured plate provided at a junction between the stuffing box and the tube section, the stufiing box housing means defining interstices to retard the passage of steam therethrough, and said apertured plate being constructed and arranged so that steam is injected into a straight portion of the tube section generally parallel to the waterflow therethrough.
  • said steam injecting means comprises a tube section connected to said second conduit means, and an injection nozzle adapted for connection to a source of steam arranged transversely within the tube section so as to inject steam into the latter in a direction parallel to the waterflow therethrough.
  • said steam injecting means comprises a tube section connected to said second conduit means, a crossflow tube extending diametrically across said tube section and being adapted for connection to a source of steam, and said crossflow tube housing means defining interstices for retarding the flow of steam therethrough, and a plurality of apertures in said crossflow tube for the passage of steam outwardly therefrom.
  • said steam injecting means comprises a tube section connected to said second conduit means, a tubular ring extending about the inner periphery of said tube section, said ring being provided with a plurality of apertures and being adapted for connection to a source of steam, and said ring housing means defining interstices for retarding the flow of steam therethrough.
  • said steam injecting means comprises a tube section connected to said second conduit means, an annular hollow venturi tube extending around the inner periphery of said tube section, said annular venturi tube including an innermost conical surface provided with a plurality of apertures, and said venturi tube housing means defining interstices for retarding the flow of steam therefrom.
  • a method of operating a steam generating installation which includes a stack having evaporation means including evaporatively cooled surfaces, a steam drum located above the stack, first conduit means for conducting cooled water from the steam drum to the evaporation means and second conduit means for conducting a steam-water mixture from the evaporation means to the steam drum comprising the steps of injecting steam in the form of small bubbles into the second conduit means at a position below the steam drum to establish a density differential between the cooling water in the first conduit means and the steam-water mixture in the second conduit means to achieve circulation in the system from the evaporator means through the second conduit means to the r 9 l t s r 10 steam tank and performing the latter step prior to supply sup retarding the flow of steam and generating the steam bubbles plying a heated medium to the'stacl c.
  • the method as defined' in claim 18 including the stepof injection thereof into the step mwater mixture.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Pipeline Systems (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Catching Or Destruction (AREA)
US768390A 1967-10-20 1968-10-17 Steam generating installations Expired - Lifetime US3545410A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB4788167A GB1207688A (en) 1967-10-20 1967-10-20 Improvements in and relating to steam generating installations
GB5777267 1967-12-20

Publications (1)

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US3545410A true US3545410A (en) 1970-12-08

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US768390A Expired - Lifetime US3545410A (en) 1967-10-20 1968-10-17 Steam generating installations

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US (1) US3545410A (fr)
BE (1) BE722600A (fr)
DE (1) DE1804163A1 (fr)
ES (1) ES359320A1 (fr)
FR (1) FR1588715A (fr)
SE (1) SE340815B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110274851A1 (en) * 2010-05-10 2011-11-10 Mitsubishi Materials Corporation Apparatus for producing polycrystalline silicon
US20130036720A1 (en) * 2010-05-20 2013-02-14 Kenta Haari Gasification power generation plant

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110274851A1 (en) * 2010-05-10 2011-11-10 Mitsubishi Materials Corporation Apparatus for producing polycrystalline silicon
US9315895B2 (en) * 2010-05-10 2016-04-19 Mitsubishi Materials Corporation Apparatus for producing polycrystalline silicon
US20130036720A1 (en) * 2010-05-20 2013-02-14 Kenta Haari Gasification power generation plant
US9429043B2 (en) * 2010-05-20 2016-08-30 Mitsubishi Hitachi Power Systems, Ltd. Gasification power generation plant

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Publication number Publication date
DE1804163A1 (de) 1969-06-19
ES359320A1 (es) 1970-08-16
BE722600A (fr) 1969-04-18
FR1588715A (fr) 1970-04-17
SE340815B (fr) 1971-12-06

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